1. Technical Field
This invention relates to a method of displaying the machining time of a simultaneous four-axis lathe and, more particularly, to a simultaneous four-axis lathe machining time display method for displaying, in the form of a bar graph, the machining time of each tool rest of the lathe using a character display unit.
2. Background Art
An NC four-axis lathe is provided with first and second NC programs corresponding to respective ones of first and second tool rests and having queuing commands. While synchronization is achieved by the queuing commands, movement of the corresponding tool rests is controlled independently by the first and second NC programs to subject a workpiece to machining.
FIG. 1 shows an example of first and second NC programs 1, 2 of this type. The programs respectively include program numbers 1a, 2a, program portions 1b, 2b for executing a first machining operation, first queuing commands 1c, 2c, program portions 1d, 2d for executing a second machining operation, second queuing commands 1e, 2e, program portions 1f, 2f for executing a third machining operation, third queuing commands 1g, 2g, program portions 1h, 2h for executing a fourth machining operation, fourth queuing commands 1i, 2i, program portions 1j, 2j for executing a fifth machining operation, and tape end commands 1k, 2k.
In accordance with the first and second NC programs 1, 2, the first and second tool rests machine a workpiece simultaneously (simultaneous independent operation) according to the program portions 1b, 2b, and, in response to the first queuing command "M100", the tool rest which finishes the machining operation first waits until the other NC controller reads in the first queuing command "M100".
When the other NC controller reads in "M100", the simultaneous independent operation is performed according to the program portions 1d, 2d. In response to the second queuing command "M200", the tool rest which finishes the machining operation first waits until the other NC controller reads in the second queuing command "M200".
When the other NC controller reads in "M200", the simultaneous independent operation is performed according to the program portions 1f, 2f. Note that since the program portion 1f is blank, the first tool rest immediately assumes a waiting state in response to the third queuing command "M300", and only the second tool rest performs machining according to the program portion 2f.
When machining by the second tool rest ends and the third queuing command "M300" is read in, the simultaneous independent operation starts in accordance with the program portions 1h, 2h. Thereafter, this four-axis lathe control is performed in a similar manner, with simultaneous four-axis machining being ended in response to the tape end commands M30.
Thus, with a four-axis lathe having two tool rests, the tool rests can be controlled and moved independently. Such a lathe is advantageous in that e.g. the outer diameter of a workpiece 13 can be cut by a tool 12 mounted on one tool rest 11 (see FIG. 2) and the inner diameter of the workpiece can be cut by a tool 22 mounted on the other tool rest 21. This enables machining time to be curtailed.
The NC programs of such a simultaneous four-axis lathe are prepared automatically in conversational fashion by the automatic programming function of an NC unit or by a separately provided automatic programming unit. It is arranged so that the machining times involved in the synchronized processes performed by the tool rests in accordance with the prepared NC programs can be displayed. It should be noted that a "synchronized process" refers to a machining process executed from one queuing command to the next.
FIG. 3 is an example of a display according to the prior art showing the cutting time and rapid-traverse time of each tool rest in each of the synchronized processes. In FIG. 3, NO. represents a synchronized process number. A process extending from an i-th queuing command to the next queuing command shall be referred to as an i-th synchronized process.
In FIG. 3, the first synchronized process is drilling performed solely by tool rest 1. The cutting time displayed for this process is 30 seconds, and that for the rapid-traverse time is 9 seconds.
The second synchronized process is outer diameter roughing performed solely by the tool rest 2, for which the cutting time displayed is 18 seconds and the rapid-traverse time 7 seconds.
The third synchronized process involves inner diameter roughing and outer diameter roughing performed simultaneously by the first and second tool rests 1, 2, respectively. The cutting time and rapid-traverse time displayed for inner diameter roughing are 1 minute 10 seconds and 18 seconds, respectively, and the cutting time and rapid-traverse time displayed for outer diameter roughing are 55 seconds and 18 seconds, respectively. The machining times for the other synchronized processes performed by the tool rests are displayed in a similar manner.
Displayed lastly are the total cutting time and total rapid-traverse time using the longer of the cutting and rapid-traverse times of the processes performed simultaneously by the tool rests 1 and 2.
With this conventional method of displaying machining times, however, the machining time of each synchronized machining process performed by each lathe is displayed in the form of characters. For this reason, the displayed times are difficult to read and it is difficult to ascertain where time is being wasted and to what extent machining is being performed simultaneously.